1. Field of the Invention
This invention relates to a shield tunnelling machine provided with a rotor turned around a first axis extending in axial direction of a shield body and rotated around a second axis eccentric to the first axis.
2. Description of the Prior Art
One shield tunnelling machine of this kind is disclosed in Japanese Patent Disclosure (KOKAI) No. 61-102999 and No. 63-189596. This excavating machine comprises a tubular shield body; a partition wall for defining the interior of the body into a front region and a rear region; a rotor disposed in the front region so as to permit the turning motion around an axis of the body and the rotational motion around an axis displaced from the axis of the body and having an outer surface gradually increasing in diameter toward the rear; a drive mechanism for turning and rotating the rotor; an excavating cutter assembly connected to the rotor so as to be turned and rotated together with the rotor; and a discharging mechanism for discharging the excavated matter from the front region to the rear region.
The front region has a first chamber having a diameter gradually decreasing toward the rear that receives the matter excavated by the cutter assembly and a second chamber communicating with a rear portion of the first chamber to receive the excavated matter from the first chamber and extending around the axis of the body. The rotor has an outer diameter gradually increasing toward the rear and is disposed in the first chamber.
In excavation, the rotor and the cutter assembly are turned around the axis of the body and rotated around the axis eccentric to the axis of the body by the drive mechanism. In this manner, the cutter assembly excavates a facing, and the rotor serves as a machine for compacting and crushing the excavated matter in cooperation with the body. During excavation, the first and second chambers are filled with the excavated matter, thereby preventing collapse of the facing.
In this known tunnelling machine, however, pressurized muddy water is supplied from the rear region to the second chamber. As the muddy water and the excavated matter in the second chamber are discharged to the rear region, the problem of separation of discharged muddy water and excavated matter prior to water disposal exists.
In order to solve the problem when a discharging mechanism is provided with a screw conveyor to excavate ground containing a large quantity of highly viscous matter, like a silt layer, the excavated matter is particularly prevented from shifting through the second chamber toward the discharging mechanism due to the viscosity of the excavated matter, so that the excavated matter is not discharged to make continued excavation difficult.